Systems and Methods for Powering Devices with a Thermoelectric System

ABSTRACT

A system for powering a micro-robot including a thermoelectric system integrated with the micro-robot wherein the thermoelectric system includes a thermopile. A rechargeable battery operatively connected to the thermoelectric system to recharges the rechargeable battery using electricity generated by the thermopile from an environmental temperature gradient.

RELATED APPLICATION DATA

The present application claims priority to U.S. Provisional ApplicationNo. 60/704,838 entitled “Systems and Methods for Powering Devices with aThermoelectric System,” filed on Aug. 2, 2005.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

The U.S. Government has a paid-up license in this invention and theright in limited circumstances to require the patent owner to licenseothers on reasonable terms as provided for by the terms of Contract No.OF8630-03-C-0133 awarded by the U.S. Department of Defense.

TECHNICAL FIELD

This invention relates generally to the field of thermoelectricgenerators and more particularly to the use of thermoelectric generatorsto power micro-robots and other micro-devices. BACKGROUND OF THEINVENTION

Miniaturized robots, also mown as micro-robots, may be used in numeroussituations and locations to receive and transmit data communications andperform various other requirements. Micro-robots may be positioned inremote locations to either transmit images or sounds or other types ofdata. Micro-robots may be used for commercial or military applications.For instance, in a commercial application, micro-robots may be used tolocate and identify personnel trapped within buildings as a result ofearthquake or terrorist attack. The micro-robots are sufficiently smallenough to maneuver within the collapsed structure and navigate withinvery small confinements. Micro-robots may use various methods formaneuvering to its destination, including but not limited to hopping,vibrating, and rolling. Micro-robots currently rely upon “buttonbatteries” for power supplies. The operational time for which suchtraditional button batteries can supply power is measured in hours.Therefore, without an improved system or method for providing extendedpower to the micro-robots, the use of micro-robots becomes extremelylimited. In order for the micro-robots to operate over a long period oftime, it will be necessary for the micro-robots to be able to rechargetheir batteries within the environment for which they are located. Forexample, within a collapsed structure, the only source of reliable poweris heat. Optimally, a number of potential heat sources should beavailable to ensure rapid location of such power supplies.

Therefore, there is a need in the art for systems and methods forproviding extended power supply to micro-robots through the use of heatenergy sources.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of the Seebeck Effect for thermoelectric systemsaccording to an exemplary embodiment of the present invention.

FIG. 2 is a thermopile of the thermoelectric system according to anexemplary embodiment of the present invention.

FIG. 3 is an exemplary plot of ground and atmospheric temperatures.

FIG. 4 is a hopping micro-robot for use with the thermoelectric systemaccording to an exemplary embodiment of the present invention.

FIG. 5 is a flow chart of the operation of a thermoelectric systemintegrated with a micro-robot according to an exemplary embodiment ofthe present invention.

FIG. 6 is a vibrating micro-robot according to an exemplary embodimentof the present invention.

FIG. 7 is a vibrating micro-robot for use with the thermoelectric systemaccording to an exemplary embodiment of the present invention.

FIG. 8 is a mini-WHEGS micro-robot according to an exemplary embodimentof the present invention.

FIG. 9 is a scout micro-robot according to an exemplary embodiment ofthe present invention.

FIG. 10 is an infrared sensor for a micro-robot according to anexemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawing, in which an exemplary embodimentof the invention is shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, this embodiment is provided sothat this disclosure will be thorough and will fully convey the scope ofthe invention to those skilled in the art. Like numbers refer to likeelements throughout.

As illustrated in FIG. 1, continuously flowing electrical current may becreated when a first wire 12 of a first material is joined with a secondwire 14 of a second material and then heated at one of the junction ends16. This is known as the Seebeck Effect. The Seebeck effect has two mainapplications: Temperature Measurement (thermocouple) and PowerGeneration. A thermoelectric system is one that operates on a circuitthat incorporates both thermal and electrical effects to convert heatenergy into electrical energy or electrical energy to a decreasingtemperature gradient. The combination of the two or more wires creates athermopile 10 that is integrated into a thermoelectric system. Whenemployed for the purposes of power generation, the voltage generated isa function of the temperature difference and the materials of the twowires used. A thermoelectric generator has a power cycle closely relatedto a heat engine cycle with electrons serving as the working fluid andcan be employed as power generators. Heat is transferred from a hightemperature source to a hot junction and then rejected to a lowtemperature sink from a cold junction or directly to the atmosphere. Atemperature gradient between the temperatures of the hot junction andthe cold junction generates a voltage potential and the generation ofelectrical power. Semi-conductors may be used to significantly increasethe voltage output of thermoelectric generators.

FIG. 2 illustrates a thermopile 20 constructed with an n-typedsemiconductor material 22 and a p-type semiconductor material 24. Forincreased electrical current, the n-type materials 22 are heavily dopedto create excess electrons, while p-type materials 24 are used to createa deficiency of electrons. The thermopile 20 is not limited to thisconfiguration and may be any thermopile sufficient to generateelectricity from a temperature gradient.

Thermoelectric generator technology is a functional, viable andcontinuous long-term electrical power source. Thermoelectric generatorsmay be coupled with rechargeable battery technology, capacitortechnology, or a combination of rechargeable batteries and capacitors toprovide extended power supplies to micro-robots and other micro-devices.

Due to the accessibility of temperature gradients occurring in naturaland man-made environments, thermoelectric generators can provide acontinuous power supply for devices in need of a power source. One ofthe most abundant, common, and accessible sources of energy isenvironmental heat. In buried hardened target environments,environmental heat may be the only feasible source of energy.

Micro-robots may be used in numerous commercial and military conditionsin environments which are very difficult to access, including hardenedtarget environments, for payload delivery or other reconnaissanceoperations. Micro-robots include numerous and varying forms includingbut not limited to hopping micro-robots, vibrating micro-robots, walkingmicro-robots, and rolling micro-robots. Due to the remote operationallocation of many micro-robots, recharging of the batteries of amicro-robot may prove difficult. Thermoelectric systems may be employedto provide power to micro-robots. The thermoelectric system may includea thermoelectric generator that may be integrated with a micro-robot toprovide electrical power. The thermoelectric generator includes athermopile. In an exemplary embodiment, the thermopile is of theconfiguration of FIG. 2. Again, the thermopile is not limited to theconfiguration of FIG. 2 and may be any thermopile sufficient to generateelectricity from a temperature gradient.

Heat energy may be extracted from a number of environmental sourcesthereby allowing for a number of potential “power stations” for themicro-robot. In addition to natural environmental sources, Table 1illustrates numerous heat sources that the thermoelectric system of amicro-robot may employ. TABLE 1 APPROX. MAXIMUM ENVIRONMENTAL HEATSOURCE TEMPERATURE (F. °/C. °)* OFFICE SOURCES Computer Power Unit(internal) 100/40  Computer Screen (CRT) (internal) 110/45  CoffeeMakers 195/91  AC Units 80/30 Generators (Electrical) 140/60  Heaters(i.e. steam @ 25 psig) 266/130 Televisions (internal) 110/44 Refrigerator Compressors 90/30 Stoves 500/260 Ovens 500/260 Hot WaterHeaters (Gas) 2500/1370 Dishwashers 140/60  LABORATORY SOURCESAutoclaves 250/120 Hot Plates 450/230 Mixing Equipment 190/90  PowerGenerators 325/165 Hot Water Pipes 140/55  Steam Pipes (@ 25 psig)266/130

In the absence of heat sources such as those listed in Table 1, thethermoelectric generator may use the thermal differential between theearth's surface and the earth's temperature as low as a foot below theearth's surface for a temperature gradient sufficient to create adequateelectrical energy for a micro-robot. FIG. 3 illustrates a plot of atemperature differential between the atmosphere at the earth's surfaceand 30 centimeters below the earth's surface. The plot of FIG. 3illustrates temperatures present at Royston, Hertfordshire in March2000. One of ordinary skill in the art will appreciate that FIG. 3 isfor illustrative purposes only and does not represent the temperaturegradient at all locations on earth and at all times.

As shown in FIG. 3, at certain times the atmospheric temperature isgreater than the subsurface temperature and at other times theatmospheric temperature is less than the subsurface temperature.However, for the thermoelectric generator to produce electricity only atemperature differential is required and, therefore, can produceelectricity in either scenario. Generally, until a depth greater than300 feet is reached, the temperature of the earth tends to decrease withdepth. Thus, with a larger probe with higher surface area and greaterdepth into the earth surface, higher amounts of energy can be generateddue to an increased temperature gradient with the earth's atmosphericconditions at the surface.

The temperature gradient used to generate electrical energy may also beobtained from extreme conditions at the location of the micro-robot. Forexample, if a building is collapsed or on fire, the micro-robot may usethe heat from the building or fire to create a temperature gradient topower the micro-robot. One of ordinary skill in the art will appreciatethat any high heat source may be used to generate a temperature gradientto power the micro-robot.

FIG. 4 illustrates an exemplary embodiment of a hopping micro-robot 40.In this exemplary embodiment, the hopping micro-robot 40 navigates andmaneuvers through use of a hopping mechanism including a bottom leg 42and a top leg 44. The hopping micro-robot may include a rechargeablebattery 46 to provide electrical power. The rechargeable battery 46 maybe located on the top leg 44 or any other location on the hoppingmicro-robot to supply power thereto. A thermopile 48 may be integratedwith the micro-robot.

As illustrated in the flow chart of FIG. 5, the rechargeable battery maybe recharged through the use of the thermopile of a thermoelectricsystem integrated with the micro-robot. The thermopile 52 contacts aheat source 51 such that a temperature gradient is formed within thewires of the thermopile at step 52. The thermopile 52 then generateselectricity by converting the thermal energy in the temperature gradientto electricity at step 53. The electricity generated may then pass to atrickle charger at step 54 and the trickle charger then charges therechargeable battery at step 55. Once the rechargeable battery ischarged, the battery can provide sufficient power to the needs of themicro-robot including the steps of mobility at step 56, navigation atstep 57, or any other desired operation, such as pay load delivery atstep 59.

The thermoelectric generator also may be used to charge an on boardsuper capacitor of the micro-robot device at 58. The super capacitor maybe configured to store an abundance of electrical energy and also mayexpel the electrical energy in a slow controlled manner or in a burst ofelectricity. The super capacitor may supply power to the micro-robot andalso may provide power for any potential weapon (i.e. explosiveinitiator) in a hard/overt kill capacity or to act as a weapon itself ina covert/soft kill capacity as well. For example, the super capacitormay operate as a weapon by short circuiting a Central Processing Unit,overloading a circuit of a desired device, and initiating a fire byexpelling the abundance of electrical energy with a burst ofelectricity. One of ordinary skill in the art will appreciate that theuse of a super capacitor is not limited to the examples enumeratedherein but may be used to supply power, act as a weapon initiator, oract as a weapon itself in any manner. The thermoelectric generator alsomay be used to provide electrical energy to power any required deviceson a micro-robot, including but not limited to sensors, processors, andmechanical operations.

The recharging of the battery is not limited to the steps of FIG. 5 andmay include a system for recharging the battery that uses a thermopile.A capacitor may be used in place of a rechargeable battery to providepower to the micro-robot. The thermoelectric generator may be used tocharge the capacitor with electrical energy. One of ordinary skill inthe art will appreciate that any number of rechargeable batteries,capacitors, or combination of a rechargeable batteries and a capacitorsare contemplated herein.

The thermoelectric system may be affixed in any location on themicro-robot that allows for a temperature gradient to be exposed to thethermopile of the thermoelectric system. In an exemplary embodiment ofthe hopping micro-robot, the thermoelectric system is affixed to thebottom leg 44 such that the thermoelectric system interfaces a hotsurface to expose itself to the temperature gradient between the hotsurface and the atmosphere. The hot surface may include any material orsubstance that has a temperature higher than the atmosphere, includingthe items listed in Table 1.

The thermoelectric system also may include a stake (not shown) that canbe inserted into the ground to increase the thermal gradient with thehot surface. The thermopile may be integrated with the stake to produceelectricity from the temperature gradient. One of ordinary skill in theart will appreciate that the thermoelectric system may be affixedanywhere on the micro-robot that is exposed to a temperature gradient.

In another exemplary embodiment, the thermoelectric system may provideelectrical energy to a vibrating micro-robot 60 as illustrated in FIG.6. The vibrating micro-robot employs vibration (or micro-hopping) as alocomotion mechanism. Similar to the hopping micro-robot embodiment,thermoelectric system may be used to provide electrical energy tooperate the locomotion of a vibrating micro-robot. The micro-robot 60may employ a rechargeable battery 62 that powers vibrating motors 64.The vibrating motors 64 vibrate to move the micro-robot 60 in a desireddirection. A sensor 66 and related microprocessor and circuitry may beintegrated in the vibrating micro-robot 60 to instruct the micro-roboton its destination. The sensor 66 may be any sensor capable of detectinga heat source such as an infrared sensor, heat sensor, or other lightsensor.

FIG. 7 illustrates an embodiment of a vibrating micro-robot 70 with anintegrated thermoelectric system 72. The thermoelectric system 72 may bepositioned on a surface of the micro-robot that interfaces the heatsource. A thermopile of the thermoelectric system could then generateelectricity from the temperature gradient between a heat source and theatmosphere. The vibrating micro-robot 70 may further include at leastone microcapacitor 74 to hold the electricity generated by thethermopile. It should be understood that the vibrating micro-robot mayalso include a rechargeable battery or any other type of battery orcapacitor. The vibrating micro-robot may further include a radiator 78for maximizing heat dissipation and increasing the heat differencebetween the hot side and cold side of the thermopile.

In addition to hopping micro-robots and vibrating micro-robots,thermoelectric generators may be used to provide electrical power to anymicro-robot including mini-WHEGS micro-robots 80 shown in FIG. 8, Scoutmicro-robots 90 shown in FIG. 9, or any other type of micro-robots ormicro device where power can be generated with a thermoelectricgenerator. One of ordinary skill in the art will appreciate that the useof thermoelectric systems to provide sufficient power to micro-robots isnot limited to the types of micro-robots disclosed herein but isapplicable to any micro-robot or micro device.

The thermoelectric system also may include a sensor for locating thermalconditions to allow for recharging the batteries or charging thecapacitors. The sensors may include heat sensors, light detectingsensors, or any other sensing device operable to determine a thermalsource. In an exemplary embodiment, the thermoelectric system mayincorporate a light tracking sensor which allows the micro-robot totrack a source of light in a dark environment. FIG. 10 illustrates anembodiment of a micro infrared seeker which can be used to identifypotential heat sources. The micro infrared sensor of the micro-robot maydirect the micro-robot to move to the light. The source of light mayprovide a sufficient temperature gradient for the thermoelectricgenerator to generate electricity. In another exemplary embodiment,infrared sensors may be integrated with the thermoelectric system toallow the micro-robot to autonomously locate a heat source forrecharging the battery or capacitor. The thermoelectric generator may beused to power the sensor as well as locomotive components of themicro-robot. The sensors alternatively may be powered by an auxiliarybattery. The thermoelectric system may also include a device thatdetermines how much power remains in the battery or capacitor thatpowers the micro-robot. The amount of remaining power may be used todetermine if recharging of the battery or capacitor is needed.

The thermoelectric system may further include a microprocessor forguidance, command, and control of the sensors and the micro-robot. In anexemplary embodiment, based on the operational parameters desired, themicroprocessor of the thermoelectric system may be programmed todetermine the best available source of thermal heat in order todetermine the most efficient means for recharging the batteries. If arapid charge is required, the microprocessor may command the micro-robotto locate a thermal source that creates a large temperature gradient.Likewise, if a rapid charge is not required, the microprocessor may beprogrammed to command the micro-robot to find a less conspicuouslocation to charge the battery or capacitor. One of ordinary skill inthe art will appreciate that the microprocessor does not have to be partof the thermoelectric system. A microprocessor on the micro-robot may beprogrammed to guide, command, and control the micro-robot and thesensors. One of ordinary skill in the art will appreciate that standardguidance and control techniques may be implemented to guide and controlthe micro-robots movement to the heat source.

In addition to micro-robots, the thermoelectric generators may be usedto power other devices that require power over extended periods of time.In the exemplary embodiment of FIG. 11, a thermoelectric system may beused to power a weather station 1100 or the individual components of aweather station. An illustration of a weather station is shown in FIG.11. In order to conserve power, the invention proposes the “seeding” oflarge areas with dozens (or hundreds) of individual sensors (i.e.humidity sensors, temperature sensors, wind velocity sensors, winddirection sensors, etc.) which in and of themselves consume littlepower. Micro-transmitters may be connected to sensors which mayperiodically send data to a central data fusion center and a broadpicture of the environmental conditions over a wide area could bepainted, thereby providing a more accurate weather account than anindividual weather station. The sensors require little power and may bepowered by the thermal gradient between the surface of the earth and thesub-surface of the earth. In an exemplary embodiment, the thermalgradient may be achieved through a sub-surface depth of between one andthree feet. One of ordinary skill in the art will appreciate that anysub-surface depth that creates a temperature gradient is contemplatedherein.

The weather stations 1100 are often used in remote locations and may berequired for use for an amount exceeding the battery life. Thethermoelectric generator may be used to provide electrical power to theweather station. In an exemplary embodiment, the weather station restson the earth's surface. The thermoelectric system may include a stakethat is inserted into the earth's surface. The temperature of the earthgenerally decreases with depth at depths up to 100 feet. Therefore, thetemperature at the end of the stake is typically lower than thetemperature at the earth's surface. The difference between thetemperature at the end of the stake and the earth's surface provides thetemperature gradient sufficient for creating electrical energy throughthe thermopile of the thermoelectric system. One of ordinary skill inthe art will appreciate that the temperature gradient may be attainedfrom any source and is not limited to the use of a stake in the ground.

In another embodiment of the present invention, the thermoelectricsystem may be integrated with an unattended ground sensor. An unattendedground sensor may be used for a number of applications such as intrusiondetection, sound detection, IR detection, etc. The sensor would becoupled with a miniature RF transmitter (as would the previouslyreferenced weather sensors) and would transmit its data to a centraldata collection command post to alert authorities in the event ofintrusion into restricted areas.

It should be apparent that the foregoing relates only to exemplaryembodiments of the present invention and that numerous changes andmodifications may be made herein without departing from the spirit andscope of the invention as defined herein.

1. A system for powering a micro-robot comprising: a thermoelectricsystem integrated with the micro-robot, wherein the thermoelectricsystem comprises a thermopile; and a rechargeable battery operativelyconnected to the thermoelectric system, wherein the thermoelectricsystem recharges the rechargeable battery using electricity generated bythe thermopile from an environmental temperature gradient.
 2. The systemof claim 1 wherein the micro-robot is chosen from a group consisting ofa hopping micro-robot, vibrating micro-robot, mini-WHEGS micro-robot,and scout micro-robot.
 3. The system of claim 1 wherein theenvironmental temperature gradient is the difference in temperaturebetween a heat source and the atmosphere.
 4. The system of claim 3wherein the heat source is chosen from a group consisting of computers,monitors, Air Conditioning units, generators, televisions,refrigerators, stoves, ovens, hot water heaters, dishwashers,autoclaves, hot plates, mixing equipment, hot water pipes, steam pipes,and the earth's surface.
 5. The system of claim 1 wherein theenvironmental temperature gradient is the difference in temperaturebetween earth's surface and the earth's subsurface.
 6. The system ofclaim 1 further comprising a sensor for detecting a heat source.
 7. Thesystem of claim 6 further comprising a microprocessor for guidance andcontrol of the micro-robot to the heat source identified by the sensor.8. The system of claim 7 wherein the sensor is an infrared sensor.
 9. Asystem for powering a micro-robot comprising: a thermoelectric systemintegrated with the micro-robot, wherein the thermoelectric systemcomprises a thermopile; and a capacitor operatively connected to thethermoelectric system, wherein the thermoelectric system charges thecapacitor using electricity generated by the thermopile from anenvironmental temperature gradient.
 10. The system of claim 9 whereinthe micro-robot is chosen from a group consisting of a hoppingmicro-robot, vibrating micro-robot, mini-WHEGS micro-robot, and scoutmicro-robot.
 11. The system of claim 9 wherein the environmentaltemperature gradient is the difference in temperature between a heatsource and the atmosphere.
 12. The system of claim 11 wherein the heatsource is chosen from a group consisting of computers, monitors, AirConditioning units, generators, televisions, refrigerators, stoves,ovens, hot water heaters, dishwashers, autoclaves, hot plates, mixingequipment, hot water pipes, steam pipes, and the earth's surface. 13.The system of claim 9 wherein the environmental temperature gradient isthe difference in temperature between earth's surface and the earth'ssubsurface.
 14. The system of claim 9 further comprising a sensor fordetecting a heat source.
 15. The system of claim 14 further comprising amicroprocessor for guidance and control of the micro-robot to the heatsource identified by the sensor.
 16. The system of claim 15 wherein thesensor is an infrared sensor.
 17. The system of claim 9 wherein thecapacitor is a super capacitor capable of rapid discharge.
 18. A methodfor powering a micro-robot comprising: integrating a thermoelectricsystem with the micro-robot; and recharging a battery of the micro robotusing electricity generated by the thermoelectric system, whereinthermoelectric system generates electricity from an environmentaltemperature gradient.